Flexible seal between roof and sidewalls of a steam generator furnace

ABSTRACT

A gastight flexible seal structure connecting the vertical tubular sidewalls with the tubular roof at their line of intersection, with the various parts thereof including: a skin casing covering the upper surface of the roof tubes; a gastight vertical seal structure sealing the space between the sidewall tubes from air or gas leakage with this seal structure terminating a predetermined distance above the roof elevation; a first flexible seal plate having one edge scalloped and seal welded to the sidewall tubes and the above vertical seal structure, and having a generally upright portion freely extending along the furnace-facing side of the sidewall tubes; and a second seal plate having its upper edge seal welded to the upright portion of the first seal plate and its bottom edge seal welded to the roof skin casing, and with the upper part forming an angle with the vertical and the lower part being bent outwardly from the sidewall tubes with respect to the lower part.

United States Patent Suhs [ 1 Feb. 29, 1972 [54] FLEXIBLE SEAL BETWEEN ROOF AND SIDEWALLS OFASTEAM GENERATOR FURNACE [72] Inventor: Gerhard W. Suhs, Longmeadow, Mass.

[73] Assignee: Combustion Engineering, Inc., Windsor,

Conn.

[22] Filed: Oct. 19, 1970 211 App]. No.1 81,771

Primary Examiner-Kenneth W. Sprague Attorney-Carlton F. Bryant, Eldon H. Luther, Robert L. 01- son, John F. Carney, Richard H. Bemeike, Edward L. Kochey, Jr. and Lawrence P. Kessler [57] ABSTRACT A gastight flexible seal structure connecting the vertical tubular sidewalls with the tubular roof at their line of intersection, with the various parts thereof including: a skin casing covering the upper surface of the roof tubes; a gastight vertical seal structure sealing the space between the sidewall tubes from air or gas leakage with this seal structure terminating a predetermined distance above the roof elevation; a first flexible seal plate having one edge scalloped and seal welded to the sidewall tubes and the above vertical seal structure, and having a generally upright portion freely extending along the furnace-facing side of the sidewall tubes; and a second seal plate having its upper edge seal welded to the upright portion of the first seal plate and its bottom edge seal welded to the roof skin casing, and with the upper part forming an angle with the vertical and the lower part being bent outwardly from the sidewall tubes with respect to the lower part.

10 Claims, 7 Drawing Figures PATENTEDFEB 29 I972 SHEET 1 BF 2 GERHARD W. SUHS AGENT PMENTEBFEBZSIQYZ 3,645,238

SHEET 2 [1F 2 F166 FIG? GERHARD W. SUHS INVENTOR.

BYE/4M? AGENT FLEXIBLE SEAL BETWEEN ROOF AND SIDEWALLS OF A STEAM GENERATOR FURNACE BACKGROUND OF THE INVENTION The invention generally relates to a steam generator, and more particularly to a flexible structure for sealing against gas or air leakage at the roof of the generator at the line of intersection with the sidewalls.

In the past, the roof casing was seal welded to a sidewall casing enclosing the portion of the sidewall tubes on both sides between the roof elevation and the upper sidewall headers and being welded to the headers. This construction proved to be inadequate, since it required stress relieving of the headers. Furthermore, in the operation of the unit the casing and welded connections being subject to thermal expansion stress and lacking flexibility, would cause the casing to bulge and break the weld connection, permitting leakage between the exterior and the interior of the furnace.

Modern steam generator designs require that the furnace and adjacent gas passages be surrounded by a gastight envelope capable of resisting the static pressure difference which exists during operation between the furnace interior and the outside atmosphere or pressurized roof enclosure. At the same time, due to the difference in temperatures occuring between adjoining portions of this envelope, such as between the roof casing and the sidewalls, seal structures must be provided between these portions which are flexible as well as sturdy enough to permanently prevent gas or air leakage, by withstanding both the stresses due to the static pressure difference and the stresses caused by thermal expansion between adjoining envelope portions.

Furthermore, it is very important that such seal structures be characterized by simplicity of fabrication, reliability during operation, and easy accessibility of field welds without stress relieving of headers or other pressure parts.

SUMMARY OF THE INVENTION The seal structure disclosed herein possesses the necessary features designed to overcome the above difficulties by providing a skin casing in contact with the upper surface of the roof tubes, a gastight sealing means, such as a skin casing, tube fins or fusion welded seams, sealing the space between the sidewall tubes from gas leakage, with this means extending and tenninating a predetermined distance above the roof casing. In connection and in cooperation with the above, the invention provides a first flexible seal plate on the furnace side of the sidewall tubes and generally parallel thereto, having one edge scalloped and fitted around the sidewall tubes and seal welded to the tubes and to the above sealing means, and having an upright freely extending portion. Furthermore, a second upwardly extending flexible seal plate is provided with a bottom edge seal welded to the roof skin casing and with an upper edge seal welded to the upright portion of the first seal plate. To impart flexibility the first seal plate or the upper portion of the second seal plate fonns an angle of from -l0 with the vertical, and a lower portion of the second seal plate forms an angle of at least with the vertical.

The above combination results in a sealing structure characterized by simple construction and fabrication. It further possesses reliability in operation and good flexibility in the horizontal direction and also some flexibility in the vertical direction. Furthermore, the first seal plate with the scalloped lower edge seal welded to the tubes in the shop also serves as a supporting band when shipping the tubes assembled in tube panels from the shop to the erection site. The disclosed seal structure in addition resists internal pressure with a minimum of stiffness. It eliminates stress relieving of the sidewall headers and permits savings in sidewall casing costs over earlier designs which require the extension of the casing above the roof elevation to the upper sidewall header.

It is accordingly a primary object of the invention to provide a sealing structure which affords a maximum of flexibility coupled with sufficient stiffness to resist internal pressure.

It is another object of the invention to provide a seal structure which is simple in fabrication and reliable in operation due to easily accessible field welds and does not require stress relieving of pressure parts.

Other objects and advantages of the invention will become apparent to those skilled in the art as the description hereof proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial elevational cross section of a steam generator showing the roof and upper sidewall.

FIG. 2 is an enlarged cross section taken on line 2-2 of FIG. 1 showing the seal structure at the line of intersection between a plane at the roof elevation and the solidly welded tubes of the left-hand sidewall.

FIG. 3 is an enlarged cross section taken on line 33 of FIG. 1 and similar to FIG. 2; however, showing the seal structure applied to sidewall tubes supplied with a skin casing.

FIG. 4 is an enlarged cross section taken on line 4-4 of FIG. 1 showing a seal structure similar to that shown in FIG. 2, except with the upright portion of the first seal plate extending downwardly instead of upwardly.

FIG. 5 is an enlarged cross section taken on line 5-5 of FIG. 1 showing a seal structure similar to that shown in FIG. 3, except with the upright portion of the first seal plate extending downwardly instead of upwardly.

FIG. 6 is a cross section through the sidewall and seal structure when taken on line 6-6 of FIG. 2, showing one scalloped bar seal welded to the tubes of a solidly welded wall.

FIG. 7 is a cross section through the sidewall and seal structure when taken on line 77 of FIG. 3, showing two scalloped bars seal welded to the tubes of the sidewall provided with a skin casing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings wherein like reference characters are used throughout to designate like elements, the illustrative and preferred embodiments of the invention depicted therein include a steam generator designated generally as 10 and comprising a furnace chamber 12 lined with heat-absorbing tubes. These tubes include front wall tubes 14, and roof tubes 16 which terminate in a steam-and-water drum or mixing header l8 and rear wall tubes 19. They also include widewall tubes 20 which terminate in upper sidewall header 22.

In the illustrative embodiment the roof tubes 16 are provided with fins and are covered with a skin casing 24 with the space between the fins and the casing being filed with refractory. Two specific types of sidewall tubes generally designated 20 in FIG. 1 are shown. Sidewall tubes 20a which are components of a solidly welded waterwall such as shown in FIGS. 2, 4 and 6, and sidewall tubes 20b which preferably are pegfinned tubes covered with a skin casing 26 as shown in FIGS. 3, 5 and 7. Thus, the difference between these two types of tube walls lies in the means used to form a gastight seal between the tubes. In a sidewall constructed of tubes 20a as shown in FIGS. 2, 4 and 6, these means consist of a welding head or narrow band 25 uniting each two adjacent tubes to form a continuous solid wall. In a sidewall constructed of tubes 20b, as shown in FIGS. 3, 5 and 7, the gastight sealing means are represented by a skin casing 26 for sealing the plurality of sidewall tubes 20b from gas leakage therebetween. Both sealing means 25 and 26 terminate a predetermined distance above the roof elevation as indicated at 28. In contrast to earlier designs sealing means 25 or casing 26 will therefore not be required throughout the area of the sidewall between elevation 28 and header 22, which reduces sidewall manufacturing and erection costs. Furthermore, the casing need not be seal welded to the sidewall header, thereby eliminating stress relieving of the header.

The upper end of skin casing 26 is bent outwardly to provide flexibility as shown in FIGS. 3 and 5, and forms a flange which is connected to a seal bar 30. This seal bar follows the slope of the roof and has a scalloped edge fitted around the tubes 20b as shown in FIG. 7, and is seal welded thereto in the shop. In addition, both embodiments FIG. 2 and FIG. 3, a first flexible seal plate 32 is provided on the furnace side of sidewall tubes 20 which follows the slope of the roof. This plate has a generally horizontally extending lower scalloped edge 33 fitted and seal welded to tubes 20a and 20b. It is also seal welded to the scalloped edge of seal bar 30 in the embodiment of FIG. 3, and to the weld bead or welded bar 25 forming the sealing means between tubes 20a of the embodiment of FIG. 2. Seal plate 32 also has an upper portion 34 extending from the scalloped welded lower end upwardly along the tubes a short distance such as four to six inches. This upper portion 34 is not attached to the tubes except at its lower end and is therefore free to swing away from the tubes.

To establish a flexible and gastight connection between the sidewall and roof, a second seal plate 36 is provided. This plate extends from a flange 37, seal welded in the field to the roof skin casing 24, to the top edge 38 of the first seal plate 32 to which it is also seal welded in the field. In order to impart flexibility to seal plate 36, the upper portion 40 thereof is designed to form an angle of from -l0 with the vertical, and the lowerportion 42 thereof to form an angle of more than with the vertical.

The embodiments illustrated in FIGS. 4 and 5 show a seal design similar to that of FIGS. 2 and 3, also as applied to the two sidewall construction shown in FIGS. 6 and 7. The embodiments of FIG. 4 and FIG. 5 differ from those of FIG. 2 and FIG. 3, respectively, in that the seal plate 32 of FIGS. 2 and 3 is made longer in FIGS. 4 and 5 and is turned upside down. It is now designated 52 and is provided with a scalloped edge 53 at the upper end instead of at the lower end. This will afford greater accessibility of this edge in the field for repairing a leak which may occur during operation of the unit. As in the FIGS. 2 and 3 design, this scalloped edge is fitted around the tubes 20 (20a and 20b) and is seal welded thereto and to the sidewall casing members 25, see FIG. 4, or seal bar 30, see FIG. 5. The lower portion of seal plate 52 extends downwardly along the furnace side of tubes 20 (20a and 20b) and preferably slopes away from these tubes at an angle of from 5l0 with the vertical. The lower edge of seal plate 52 is connected, such as by a seal weld 54, to a second seal plate 56. The lower portion of plate 52 preferably fonns an angle of more than 20 with the vertical and is provided with a flange 57 which in turn is seal welded to the roof casing plate 24.

While I have illustrated and described preferred embodiments of my invention, it is to be understood that such are merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What is claimed is:

l. A gastight seal structure for a steam generator having a plurality of parallel vertical sidewall tubes in a vertical plane, a plurality of parallel roof tubes in a generally horizontal plane intersecting said vertical plane at a roof elevation, wherein the improvement comprises: a roof skin casing covering and in contact with the upper surface of saidroof tubes; at gastight sealing means for sealing said plurality of sidewall tubes from gas leakage therebetween and terminating a predetermined distance above said roof elevation; a first flexible seal plate having a generally horizontally extending scalloped edge seal welded to said sidewall tubes and to said gastight sealing means and having an uprightly extending portion; a second flexible seal plate having the upper part seal welded to the upright portion of said first plate and the bottom part seal welded to said roof skin casing.

2. A gastight seal structure as defined in claim 1 wherein the upright portion of said first flexible seal plate extends upwardl and is in contact with said sidewall tubes.

3. A gastight seal structure as defined in claim I wherein the upright portion of said first flexible seal plate extends downwardly and slopes away from said sidewall tubes.

4. A gastight seal structure as defined in claim 2 wherein at least the upper portion of said second flexible seal plate forms an angle of from 5 to 10 with the vertical.

5. A gastight seal structure as defined in claim 2 wherein the lower portion of said second flexible seal plate forms an angle of more than 20 with the vertical.

6. A gastight seal structure as defined in claim 2 wherein the lower portion of said second flexible seal plate is bent outwardly from the sidewall tubes with respect to the upper portion.

7. A gastight seal structure as defined in claim 3 wherein the upright portion of said first flexible seal plate forms an angle of from 5 to 10 with the vertical.

8. A gastight seal structure as defined in claim 3 wherein said second flexible seal plate forms an angle of more than 20 with the vertical.

9. A gastight seal structure as defined in claim 1 wherein said gastight sealing means comprises a fusion weld forming a solidly welded wall of sidewall tubes.

10. A gastight seal structure as defined in claim I wherein said gastight sealing means comprises a skin casing covering and in contact with the outer surface of said sidewall tubes. 

1. A gastight seal structure for a steam generator having a plurality of parallel vertical sidewall tubes in a vertical plane, a plurality of parallel roof tubes in a generally horizontal plane intersecting said vertical plane at a roof elevation, wherein the improvement comprises: a roof skin casing covering and in contact with the upper surface of said roof tubes; a gastight sealing means for sealing said plurality of sidewall tubes from gas leakage therebetween and terminating a predetermined distance above said roof elevation; a first flexible seal plate having a generally horizontally extending scalloped edge seal welded to said sidewall tubes and to said gastight sealing means and having an uprightly extending portion; a second flexible seal plate having the upper part seal welded to the upright portion of said first plate and the bottom part seal welded to said roof skin casing.
 2. A gastight seal structure as defined in claim 1 wherein the upright portion of said first flexible seal plate extends upwardly and is in contact with said sidewall tubes.
 3. A gastight seal structure as defined in claim 1 wherein the upright portion of said first flexible seal plate extends downwardly and slopes away from said sidewall tubes.
 4. A gastight seal structure as defined in claim 2 wherein at least the upper portion of said second flexible seal plate forms an angle of from 5 to 10* with the vertical.
 5. A gastight seal structure as defined in claim 2 wherein the lower portion of said second flexible seal plate forms an angle of more than 20* with the vertical.
 6. A gastight seal structure as defined in claim 2 wherein the lower portion of said second flexible seal plate is bent outwardly from the sidewall tubes with respect to the upper portion.
 7. A gastight seal structure as defined in claim 3 wherein the upright portion of said first flexible seal plate forms an angle of from 5 to 10* with the vertical.
 8. A gastight seal structure as defined in claim 3 wherein said second flexible seal plate forms an angle of more than 20* with the vertical.
 9. A gastight seal structure as defined in claim 1 wherein said gastight sealing means comprises a fusion weld forming a solidly welded wall of sidewall tubes.
 10. A gastight seal structure as defined in claim 1 wherein said gastight sealing means comprises a skin casing covering and in contact with the outer surface of said sidewall tubes. 